Optical element, lithographic apparatus including such an optical element, device manufacturing method, and device manufactured thereby

Abstract

An optical element including an anti-reflection (AR) coating is configured to reflect Extreme-Ultra-Violet (EUV) radiation only.

1. An optical element comprising an anti-reflection coating, wherein the anti-reflection coating is configured to reflect EUV radiation and thereby improve the spectral purity of a radiation beam and the optical element is a grazing incidence mirror configured to create two reflections having a different polarization for the anti-reflection coating. 
   
   
     2. An optical element according to  claim 1 , wherein the optical element is part of a collector in a lithographic apparatus. 
   
   
     3. An optical element according to  claim 1 , wherein the anti-reflection coating is configured to prevent certain wavelengths of radiation from being reflected. 
   
   
     4. An optical element according to  claim 1 , wherein substantially only EUV radiation is reflected. 
   
   
     5. An optical element according to  claim 1 , wherein about 70–90% of EUV radiation is reflected. 
   
   
     6. An optical element according to  claim 1 , wherein the thickness of the anti-reflection coating is configured so that the optical pathlength traveled by the radiation beam through the anti-reflection coating is about ¼ λ. 
   
   
     7. An optical element according to  claim 1 , wherein an 80 nm thick CaF 2  layer is used as an anti-reflection coating. 
   
   
     8. An optical element according to  claim 1 , wherein the anti-reflection coating comprises any suitable anti-reflection material. 
   
   
     9. An optical element according to  claim 1 , wherein the anti-reflection coating is made from any of magnesium fluoride (MgF 2 ), silicon dioxide (SiO 2 ), titanium dioxide (TiO 2 ), calcium fluoride (CaF 2 ), diamond, amorphous carbon, TiN, SiC or Si 3 N 4  and combinations thereof. 
   
   
     10. An optical element according to  claim 1 , wherein the grazing incidence mirror is configured to obtain a set of angles of incidence of 5° to 7°. 
   
   
     11. An optical element according to  claim 1 , wherein the two reflections are configured to occur on two sides of the grazing incidence mirror. 
   
   
     12. An optical element according to  claim 1 , wherein the grazing incidence mirror is substantially cross-shaped in order to be able to create two reflections. 
   
   
     13. An optical element according to  claim 12 , wherein the two reflections are configured to occur on two sides of the grazing incidence mirror. 
   
   
     14. An optical element according to  claim 12 , wherein the grazing incidence mirror has a substrate made of any suitable material with good heat conductivity. 
   
   
     15. An optical element according to  claim 12 , wherein the grazing incidence mirror has a substrate made of Si or Cu. 
   
   
     16. An optical element according to  claim 1 , wherein the EUV radiation is configured to be reflected on two sides of the surface of the grazing incidence mirror in order to reduce the angle of incidence. 
   
   
     17. An optical element according to  claim 1 , wherein the grazing incidence mirror comprises a substrate onto which the anti-reflection coating is coated. 
   
   
     18. An optical element according to  claim 17 , wherein the substrate is made from silicon or copper. 
   
   
     19. An optical element according to  claim 1 , wherein a material configured to suppress light at wavelengths other than that of EUV rediation is used for the anti-reflection coating. 
   
   
     20. An optical element according to  claim 19 , wherein the material is a diamond coating with a thickness of about 20–50 nm. 
   
   
     21. A lithographic apparatus, comprising:
 an illumination system configured to condition a radiation beam; 
 a support configured to support a patterning device, the patterning device being configured to impart the radiation beam with a pattern in its cross-section to form a patterned radiation beam; 
 a substrate table configured to hold a substrate; 
 a projection system configured to project the patterned radiation beam onto a target portion of the substrate; and 
 at least one optical element within the lithographic apparatus comprising an anti-reflection coating, wherein the anti-reflection coating is configured to reflect EUV radiation and thereby improve the spectral purity of the radiation beam and the optical element is a grazing incidence mirror configured to create two reflections having a different polarization for the anti-reflection coating. 
 
   
   
     22. A lithographic apparatus comprising an optical element comprising an anti-reflection coating, wherein the anti-reflection coating is configured to reflect EUV radiation and thereby improve the spectral purity of a radiation beam and the optical element is a grazing incidence mirror configured to create two reflections having a different polarization for the anti-reflection coating. 
   
   
     23. A device manufacturing method, comprising:
 providing a radiation beam; 
 patterning the radiation beam; 
 projecting the patterned radiation beam or radiation onto a target portion of a substrate; and 
 reflecting the radiation beam with at least one optical element configured to reflect EUV radiation and thereby improve the spectral purity of the radiation beam, wherein the optical element is a grazing incidence mirror configured to create two reflections having a different polarization for the anti-reflection coating. 
 
   
   
     24. A device manufactured according to the method of:
 providing a radiation beam; 
 patterning the radiation beam; 
 projecting a patterned beam of radiation onto a substrate; and 
 reflecting the radiation beam with at least one optical element configured to reflect EUV radiation and thereby improve the spectral purity of the radiation beam, wherein the optical element is a grazing incidence mirror configured to create two reflections having a different polarization for the anti-reflection coating. 
 
   
   
     25. A device manufactured according to  claim 24 , wherein the device manufactured is selected form any of: integrated circuits, integrated optical systems, guidance and detection patterns for magnetic domain memories, liquid crystal displays, and thin-film magnetic heads.